As recognized by the inventors herein, engines may utilize a turbocharger or supercharger to compress ambient air entering the engine in order to increase power. Compression of the air may cause an increase in air temperature, thus, an intercooler or charge air cooler (CAC) may be utilized to cool the heated air thereby increasing its density and further increasing the potential power of the engine. If the air at an inlet of the compressor is humid, which may occur due to one or more conditions such as humid or rainy weather conditions, decrease in ambient temperature, exhaust gas recirculation, and crankcase ventilation, water vapor may condense on the surfaces of the CAC when the intake air is cooled below the water dew point temperature. Further, when the charge air entering the CAC is boosted (e.g., an induction pressure and boost pressure are greater than atmospheric pressure), condensate may form if the CAC temperature falls below the dew point temperature. As a result, during vehicle operation, condensate may collect at the bottom of the CAC, or in the internal passages of the CAC. After a vehicle cold soak (e.g., long drive followed by an overnight soak at freezing ambient temperatures), the condensate collected within the CAC may freeze and form ice.
When the engine is started after the vehicle cold soak, ice formed in the CAC may loosen, which may eventually break free from the CAC during engine operation. During some conditions, the ice fragments that have broken free from the CAC may be captured by the throttle, resulting in icing of the throttle.
One example approach for clearing throttle-icing conditions is shown in U.S. Pat. No. 7,509,939. Therein, the throttle valve is opened and closed repeatedly in an attempt to break the ice on or around the throttle valve. However, the inventors herein have recognized potential issues with such methods. For example, the '939 patent assumes a throttle valve jammed due to ice formed on or around the throttle. In order to fracture the ice, the throttle valve is subjected to torque reversals wherein the throttle is swung back and forth repeatedly in the opening and closing directions. While attempts are made to break the ice on the ice-jammed throttle, the torque reversals do not provide sufficient time for ice particles that have broken free from the CAC and subsequently captured by the throttle to be released from the throttle. Thus, ice particles from the CAC that are captured by the throttle continue to remain on the throttle, which may impede desired throttle operation and therefore, may cause the engine to operate in a failure management mode, which severely limits engine power and causes customer dissatisfaction.
In one example, the issues described above may be addressed by a method for an engine, comprising: in response to detecting a throttle obstruction, adjusting a throttle to a fully open position; maintaining the throttle at the fully open position for a threshold duration while maintaining a desired torque; and after the threshold duration, adjusting the throttle to a desired position, the desired position based on the desired torque; wherein the throttle obstruction is detected after engine start up. In this way, by detecting the throttle obstruction after engine start up is completed, throttle obstruction resulting from ice originating from the CAC and captured by the throttle may be detected. Further, by adjusting the throttle to the fully open position, air flow through the throttle is increased, which reduces the throttle's grip on the ice fragments. Still further, by maintaining the throttle at the fully open position for a threshold duration, sufficient release time is provided for the ice fragments captured by the throttle to be released from the throttle.
As one example, during engine operation after engine startup, throttle obstruction wherein the throttle has captured ice particles, such as ice particles that detach from upstream of the throttle (e.g., in CAC) and get captured by the throttle during vehicle operation, may be detected by a controller by operating the throttle valve via a throttle motor to reach a fully closed position independent of an accelerator pedal position from a current position, and comparing the rotation speed to an expected threshold speed. Upon determining that the throttle valve has captured ice particles, the controller may signal the throttle motor to open the throttle valve to a fully open position, independent of the accelerator pedal position. After reaching the fully open position, which may be confirmed based on an indication from a throttle position sensor, the throttle valve may be maintained at the fully open position for a threshold duration. By maintaining the throttle valve at the fully open position, the ice particles captured by the throttle may be released from the throttle valve due to the increase in air flow. While the throttle is maintained open at the fully open position for the threshold duration, one or more torque reducing measures, such as spark retard, cylinder deactivation, lean fueling, displacement reduction, etc., may be undertaken to reduce any excess engine torque. Subsequently, after the threshold duration has passed, the throttle valve may be commanded to a desired position based on torque demand by a vehicle operator, which may be based on the accelerator pedal position.
In this way, by maintaining the throttle at the fully open position, airflow rate through the throttle valve may be increased, which may facilitate the removal of ice particles deposited on the throttle during engine startup after vehicle cold soak.
Torque reversals are effective for a given type of throttle icing, but are not effective for icing that can be resolved by opening the throttle during significant air flow that allows a trapped lozenge of ice (which formed upstream of the throttle) to be swept downstream of the throttle. Previous solutions have focused on crushing adhered ice. This solution adds the mitigating action of releasing the throttle's grip on unattached ice.
It should be understood that the summary above is provided to introduce in simplified form a selection of concepts that are further described in the detailed description. It is not meant to identify key or essential features of the claimed subject matter, the scope of which is defined uniquely by the claims that follow the detailed description. Furthermore, the claimed subject matter is not limited to implementations that solve any disadvantages noted above or in any part of this disclosure.